For a detailed discussion of the Birthday Problem, see the wikipedia entry
here. This solution is based
on the formula given in the "Calculating the probability" section.

Essentially we're calculating the probability that there is not a match, and then adding more
and more people thus reducing that probability until a certain threshold is met. That threshold
is (1 - minOdds) since we're calculating the probability of not matching whereas minOdds is the
probability of a match.